In recent years, it has been becoming apparent that adherent stem cells capable of differentiating into various tissues such as bones, cartilages, muscles and fats occur in bone marrow fluid, umbilical cord blood and so forth (Patent Document 1; Non-Patent Document 1; Non-Patent Document 2; Non-Patent Document 3). Adherent stem cells are capable of differentiating into a variety of cells and organs and, therefore, it is very important to have a method of efficiently separating and amplifying such cells from the viewpoint of advancement of regenerative medicine. It is reported that the frequency of occurrence of adherent stem cells is very little, namely one per 104 to 106 cells in adult bone marrow fluid (Non-Patent Document 4) and various methods of isolating, concentrating and then recovering adherent stem cell fractions have been investigated. Thus, for example, Pittenger et al. revealed the occurrence of progenitor cells capable of differentiating into fat, cartilages or bone cells in a fraction having a specific gravity of 1.073 as obtained by the Ficoll-Paque fractionation method, one of the density gradient separation methods (Non-Patent Document 4). Sekiya et al. also attempted to cause cells gravitationally fractionated by the Ficoll-Paque fractionation method to differentiate into cartilages (Non-Patent Document 5). Further, Wakitani et al. obtained fractions of cells other than erythrocytes using dextran and attempted to cause those cells to differentiate into cartilages (Non-Patent Document 6). However, the material Ficoll is not a material produced in compliance with the GMP (Good Manufacturing Practice) applicable to drugs and, therefore, cannot be used for actual medical purposes. As for the gravitational sedimentation method using dextran, dextran species produced in compliance with the standards for drugs can be used; however, adherent stem cells are separated, accompanied by other nucleated cells, in a fraction other than the erythrocyte layer and, therefore, that method is not always the best from the viewpoint of separation. Further, these methods require the procedure for washing cells several times using a centrifuge for the separation of cells from the separating liquid, although the rate of recovery of adherent stem cells is high; the procedure is complicated and the procedure is accompanied by the risk of cells being damaged by the centrifugation operation or being contaminated when the procedure is carried out in an open system. Furthermore, under the existing circumstances, no device products are available that do not require any cell washing procedure using a centrifuge or the like but can selectively isolate adherent stem cells. For such reasons, for actual separation and recovery of adherent stem cells, there are a number of reports about the case in which the bone marrow fluid or umbilical cord blood is cultured as such and, then, non-adherent cells are washed off to obtain adherent stem cells (e.g. Non-Patent Document 7).
Further, it is said that, in biological tissues such as, for example, fat, skin, blood vessel, cornea, oral cavity, kidney, liver, pancreas, heart, nerve, muscle, prostate, intestine, amnion, placenta and umbilical cord, there are stem cells from which the respective tissues originate. In recent years, however, it has been revealed that, among these stem cells, there are stem cells capable of differentiating not only into cells of the same tissue system but also into cells of another system (Non-Patent Document 8). For example, it is reported that mesenchymal stem cells collected from adipose tissues can differentiate not only into mature adipocytes but also into bone cells, cartilage cells, myoblasts, vascular endothelial cells and so forth (Non-Patent Document 9 and Non-Patent Document 10) and that dermal stem cells can differentiate into nerve cells, smooth muscle cells, adipocytes and so forth (Non-Patent Document 11). Methods of separating and recovering such biological tissue-derived multipotent stem cells are very important from the viewpoint of advancement of regenerative medicine and have the potential for leading to methods for the radical treatment of intractable stem cell exhaustion diseases, bone diseases, cartilage diseases, ischemic diseases, tissue depressions, cardiac failure and so forth. Methods in wide use for separating and collecting stem cells derived from a biological tissue generally comprise disintegrating the tissue with a digestive enzyme and then recovering cells by centrifugation (Non-Patent Document 8). Various other methods have also been investigated; for example, Hedrick et al. disclose systems and methods for recovering, treating, extracting and concentrating stem cells from adipose tissue in a container system (Patent Document 2) and systems and methods for centrifugally separating and concentrating stem cells from tissues using an automated system (Patent Document 3), among others. Yoshimura et al. disclose a method of collecting adipose tissue-derived stem cells from an aqueous solution layer, which results from liposuction, by the density gradient centrifugation method or by using ASTEC 204 (product of AMCO) (Patent Document 4) and a method of recovering such cells by using various methods, including the use of Ficoll (Patent Document 5). Hatanaka discloses a method which comprises subjecting a suspension of cells liberated from a living body-derived material to density gradient centrifugation and then capturing and recovering a specific type group of cells by passing the relevant fraction through a filter (Patent Document 6). Tabata et al. disclose a method comprising disintegrating an adipose tissue with collagenase and, after centrifugation, allowing cells to adhere to a culture dish to thereby remove leukocytes (Patent Document 7).    Patent Document 1: WO01/83709    Patent Document 2: WO2003/053346    Patent Document 3: WO2005/012480    Patent Document 4: WO2005/042730    Patent Document 5: WO2005/035738    Patent Document 6: Japanese Kokai Publication 2003-319775    Patent Document 7: WO2003/008592    Non-Patent Document 1: Pliard A. et al.: Conversion of an Immortilized Mesodermal Progenitor Cell Towards Osteogenic, Chondrogenic, or Adipogenic Pathways. J. Cell Biol. 130(6): 1461-72 (1995)    Non-Patent Document 2: Mackay A. M. et al.: Chondrogenic differentiation of cultured human mesenchymal Stem Cells from Marrow, Tissue Engineering 4(4): 415-428 (1998)    Non-Patent Document 3: Angele P. et al.: Engineering of Osteochondoral Tissue with Bone Marrow Mesenchymal Progenitor Cells in a Derivatived Hyaluronan Geration Composite Sponge, Tissue Engineering 5(6): 545-553 (1999)    Non-Patent Document 4: Pittenger. et al. Multilineage Potential of Adult Human Mesenchymal Stem Cells, Science 284: 143-147 (1999)    Non-Patent Document 5: Sekiya. et al. In vitro Cartilage Formation by human adult Stem Cells from Bone Marrow Stroma defines the sequence cellular and molecular events during chondrogenesis, Developmental Biology 7 (99): 4397-4402 (2002)    Non-Patent Document 6: Wakitani. et al. Human autologus culture expanded Bone Marrow Mesenchymal Cell Transplantation for repair of Cartilage defects in Osteoarthritic Knees, OsteoArthritis Research Society International (2002) 10, 199-206    Non-Patent Document 7: Tsutsumi. et al. Retention of Multilineage Differentiation Potential of Mesenchymal Cells During Proliferation in Response to FGF, Biochemical and Biophysical Research Communications 288, 413-419 (2001)    Non-Patent Document 8: Yasuhiko Tabata: Kokomade Susunda Saisei Iryo no Jissai (Actual State of Regenerative Medicine) (2003)    Non-Patent Document 9: Patricia A. Zuk, et al.: Multilineage cells from human adipose tissue: Implications for cell-based therapies. Tissue Engineering Vol. 7(2): 211-228 (2001)    Non-Patent Document 10: Ying Cao, et al.: Human adipose tissue-derived stem cells differentiate into endothelial cells in vitro and improve postnatal neovascularization in vivo. Biochemical and Biophysical Research Communications 332: 370-379 (2005)    Non-Patent Document 11: Toma J G, et al.: Isolation of multipotent adult stem cells from the dermis of mammalian skin. Nature cell biology 3: 778-784 (2001)